A cascade refrigeration system is typically used when relatively low temperatures are desired in a controlled environment. The cascade refrigeration system includes evaporator coils positioned within a chamber in which the environment is to be controlled. Refrigerant is supplied to the evaporator coils by a conventional compressor/condenser system. The compressor receives the refrigerant in gaseous form from the evaporator coils and compresses the refrigerant. The heat of compression is removed by the condenser and the refrigerant is provided in liquid form to an expansion valve upstream of the evaporator coils. The refrigerant returns to a gaseous state as it passes through the evaporator coils, thereby cooling the chamber in which the evaporator coils are located. In a cascade refrigeration system, a high stage is used to cool the refrigerant passing through the condenser. Refrigerant is outputted from the compressor/condenser of the high stage and passed through an expansion valve. The expanded refrigerant is delivered to the condenser in a heat exchanging relationship with the refrigerant outputted from the low stage compressor so as to cool the refrigerant outputted from the low stage compressor. Additional stages may be provided in a cascading relationship, if necessary.
By way of example, a prior art cascade refrigeration system is shown in Briggs, U.S. Pat. No. 3,590,595. The Briggs '595 patent discloses a two stage cascade refrigeration system which incorporates two heat exchangers. The heat exchangers effectuate a heat exchanging relationship between the refrigerant flowing through the low stage and the refrigerant flowing through the high stage. It is noted, however, that if one of the heat exchangers develops an internal leak, the refrigerant in the low stage and the refrigerant in the high stage will be allowed to mix. Disposal of mixed refrigerants is both difficult and expensive.
Therefore, it is a primary object and feature of the present invention to provide a cascade refrigeration system which reduces the possibility of mixing refrigerants flowing through the low and high stages of the system.
It is a further object and feature of the present invention to provide a cascade refrigeration system which is simple and inexpensive to manufacture.
It is still a further object and feature of the present invention to provide a cascade refrigeration system which accurately controls the environment within a desired chamber.
In accordance with the present invention, a cascade refrigeration system is provided. The cascade refrigeration system has a low stage having a first refrigerant flowing therethrough. The low stage includes a compressor having an input and an output, and an evaporator unit having an input operatively connected to the output of the compressor by an input conduit and an output operatively connected to the input of compressor by an output conduit. A bypass line is also provided. The bypass line has an input in communication with the input conduit of the low stage and an output in communication with the output conduit of the low stage. A bypass heat exchanger effectuates the heat exchanger relationship between the first refrigerant in the bypass line and the first refrigerant in the input conduit of the low stage.
A high stage may also be provided which has a second refrigerant flowing therethrough. The high stage includes a compressor having an input and an output, and a condenser unit having an input operatively connected to the output of the high stage of the compressor and an output operatively connected to the input of the high stage compressor by the output conduit. The second heat exchanger effectuates the heat exchanger relationship between the first refrigerant flowing through the input conduit of the low stage and the second refrigerant flowing through the output conduit of the high stage.
It is contemplated that the condenser unit of the high stage effectuate a heat exchange between the second refrigerant flowing therethrough and a fluid from a fluid source. The high stage further includes a first bypass line having an input in communication with the input conduit of the high stage and an output in communication with the output conduit of the high stage downstream of the second heat exchanger. A bypass solenoid is provided in the first bypass line of the high stage for controlling the flow of the second refrigerant therethrough.
It is contemplated that the output of the bypass line communicate with the input conduit of the low stage downstream of the second heat exchanger. The input conduit of the low stage may include a condenser unit upstream of the bypass heat exchanger for effectuating a heat exchange between the first refrigerant fluid flowing therethrough and a fluid from a fluid source.
In accordance with a still further aspect of the present invention, a cascade refrigeration system is provided. The cascade refrigeration system includes a low stage compressor having an input and an output and a low stage evaporator unit having an input and an output. A low stage input conduit operatively connects the output of the low stage compressor to the input of the low stage evaporator unit. A low stage output conduit operatively connects the output of the low stage evaporator unit to the input of the low stage compressor. A low stage refrigerant flows between the low stage compressor and the low stage evaporator unit through the low stage input and output conduits. A first bypass line has an input in communication with the low stage input conduit and an output in communication with the low stage output conduit. A bypass heat exchanger effectuates the heat exchange relationship between the low stage refrigerant flowing through the first bypass line and the low stage refrigerant flowing through the low stage input conduit.
It is contemplated that the cascade refrigeration system further include a high stage compressor having an input and an output, and a high stage condenser unit having an input and an output. A high stage input conduit operatively connects the output of the high stage compressor to the input of the high stage condenser unit. A high stage output conduit operatively connects the output of the high stage condenser unit to the input of the high stage of the compressor. A high stage refrigerant flows between the high stage compressor and the high stage condenser unit through the high stage input and output conduits. The high stage condenser unit effectuates a heat exchange between the high stage refrigerant flowing therethrough and a fluid from a fluid source. A second heat exchanger effectuates the heat exchange between the low stage refrigerant within the low stage input conduit and the high stage refrigerant within the high stage output conduit.
A second bypass line has an input in communication with the high stage input conduit and an output in communication with the high stage output conduit downstream of the second heat exchanger. A second bypass solenoid in the second bypass line controls the flow of the high stage refrigerant therethrough.
A low stage bypass valve interconnects the first bypass line to the low stage input conduit. The low stage bypass valve controls the flow of the low stage refrigerant therebetween. The low stage input conduit includes a condenser unit upstream of the bypass heat exchanger in order to effectuate a heat exchange between the low stage refrigerant flowing therethrough and a fluid from a fluid source.
In accordance with still further aspect of the present invention, a cascade refrigeration system is provided. The cascade refrigeration system includes a low stage having a first refrigerant flowing therethrough. The low stage includes a compressor having an input and an output and an evaporator unit having an input operatively connected to the output of the compressor by an input conduit and an output operatively connected to the input of the compressor by an output conduit. The cascade refrigeration system also includes a high stage having a second refrigerant flowing therethrough. The high stage includes a compressor having an input and an output and a heat exchanger having an input operatively connected to the output of the high stage compressor by an input conduit and an output conduit connected to the input of the high stage compressor by an output conduit. The heat exchanger effectuates the heat exchange between the first refrigerant within the input conduit of the low stage and the second refrigerant within the output conduit of the high stage. A bypass line has an input in communication with the input conduit of the low stage and an output in communication with the output conduit of the high stage. A bypass heat exchanger effectuates the heat exchanger relationship between the first refrigerant in the bypass line and the first refrigerant in the input conduit of the low stage.
The high stage further includes a condenser unit for effectuating an heat exchange between the second refrigerant flowing through the input conduit and a fluid from a fluid source. The high stage may also include a first bypass line having an input in communication with the input conduit of the high stage and an output in communication with the output conduit of the high stage downstream of the heat exchanger. A bypass solenoid is provided in the first bypass line in the high stage for controlling the flow of the second refrigerant therethrough.
The input of the bypass line communicates with the input conduit of the low stage downstream of the heat exchanger. A bypass valve inter connects the bypass line to the input conduit of the low stage. The bypass valve controls the flow of the first refrigerant therebetween. The input conduit of the low stage may also include a condenser unit upstream of the bypass heat exchanger for effectuating a heat exchanger between the first refrigerant flowing therethrough and a fluid from a fluid source.